Thumb collateral ligament injuries. An anatomic basis for treatment.

This anatomic and clinical study leads to the following conclusions: 1. The ulnar and radial proper collateral ligaments are the critical lateral stabilizers of the thumb MP joint; both are highly vulnerable to complete disruption, with resultant disabling joint instability. 2. The intrinsic anatomy of the radial side of the MP joint is not a mirror image of the ulnar aspect. Significant anatomic differences account for distinctive patterns of instability. Whereas disruption of the ulnar collateral ligament in conjunction with dorsal capsular tears is apt to result in combined radiovolar subluxation, disruption of the radial collateral ligament, coupled with the unopposed dynamic force of the adductor pollicis, characteristically is prone to a rapid pathologic sequence of profound joint instability, with progressive ulnar and volar subluxation and, ultimately, degenerative joint disease. 3. Optimal management of the complete collateral ligament lesion requires prompt diagnosis, most accurately confirmed with physical and radiographic stress testing, and precise surgical repair. Immobilization alone is insufficient treatment for these serious ligament disruptions, characterized by considerable displacement with wide separation of torn ends. 4. Although early direct repair affords the best opportunity for restoration of joint integrity with a highly favorable functional recovery, secondary repair and free tendon grafting, prior to joint deformity, provide consistently successful options for chronic instability.